We plan to establish a multidisciplinary research and training program focusing on khat, a psychostimulant plant widely used in Africa and the Middle East associated with significant neurobehavioral and health effects. We will use this exploratory/developmental grant to achieve two primary goals. The first is to develop collaborative relationships and provide needed capacity-building resources that will include a series of research training workshops, establishing an Institutional Review Board, conducting relevant training on ethical standards of research, and organizing semi-annual meetings to develop future programmatic research. The second goal is to complete preliminary research to determine cognitive, affective, and biobehavioral consequences of long-term khat use. Khat users and nonusers will be compared on their performance on tests of response inhibition, attention, concentration, memory, and hormonal and cardiovascular responses to acute stress. We will include two samples of khat users, those who use khat alone and those who use khat and tobacco together. The purpose will be to examine the influence of the concurrent use of both substances. The program will take advantage of a unique population and setting by conducting this work in Yemen. The design of the preliminary research is geared towards maximizing the potential for advancing khat-related research in this and surrounding countries, and will facilitate later development of research that will guide efforts to develop methods to reduce the harm caused by khat and tobacco use. The combination of measures of the stress response and cognitive functioning will provide novel information on the impact of khat use on important behavioral and neurobiological functions. We have assembled a multidisciplinary, international team with distinguished records and experience in all relevant topics. Both the training and research arms of the program will emphasize this breadth of expertise. This program will form a core part of our conceptualization of future research initiatives to further identify neurobehavioral effects of khat an concurrent tobacco use and develop means for effective intervention strategies. PUBLIC HEALTH RELEVANCE: This program addresses the growing use of khat and its harmful effects on health in many countries in Africa and the Middle East and among immigrant communities in Western Europe and North America. The program will advance our knowledge of the short and long-term effects of khat use and help guide efforts to develop future research programs related to prevention and treatment of khat and tobacco use. Combating this problem will have significant benefits on the health conditions in many countries in the world. The program will also be significant in fostering scientific and research capacity-building efforts in Yemen.